Developer compositions containing sequestering agents



United States Patent 015cc 3,467,521 Patented Sept. 16, 1969 3,467,521 DEVELOPER COMPOSITIONS CONTAINING SEQUESTERING AGENTS Karl Frank, Leverkusen, and Max Heilmann, Cologne- Flittard, Germany, assignors to Agfa-Gevaert Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Apr. 18, 1966, Ser. No. 543,038 Claims priority, application Germany, May 3, 1965,

Int. Cl. G03c 5/30 US. Cl. 96-661 3 Claims ABSTRACT OF THE DISCLOSURE Silver halide developers, the inorganic constituents of which are present in the form of their potassium salts, show less clouding during use when they contain aminoalkyl carboxylic acid derivatives, aminoalkyl phosphoric acid derivatives or aminoalkyl sulfonic acid derivatives in concentrations at least 5 times that used for sequestering calcium and magnesium.

In the preparation of solid developer mixtures, it is usual to use the cheaper sodium salts such as sodium carbonate, sodium borate or sodium sulfite. In order to be able to prepare highly concentrated developer solutions, it is in most cases necessary to use the much more readily soluble potassium salts such as potassium sulfite and potassium carbonate.

The known developer concentrates contain, for example, the following components per liter of concentrate:

G. Potassium sulfite 312 Potassium hydroxide 15 Potassium carbonate 90 Hydroquinone 45 1-phenylpyrazolidone-(3) 1.5 Potassium bromide Ethylene diaminotetracetic acid 8 A developer for photographic papers can be obtained from this concentrate by diluting it in 7 parts of water.

Such developer concentrates have, however, only a limited utility since the ready-to-use developers prepared therefrom by dilution become cloudy after some time due to atmospheric oxidation or use. The products which cause this cloudiness at first remain in suspension and so make it impossible to assess the developed image in the developing bath. On further use, the particles begin to settle and the deposit produced impairs the quality of the developed image. There has been no lack of attempts to overcome this disadvantage, but it has not hitherto been possible to prevent the cloudiness by the use of other additives.

It is the object of the invention to produce developer concentrates which remain clear upon use in working solution and which satisfy the requirements of photographic practice.

It has now been found that cloudiness in developers which have been prepared by diluting developer concentrates containing potassium salts can be prevented by adding to the concentrates relatively large quantities of compounds of the aminoalkylcarboxylic acid, aminoalkylphosphoric acid or aminoalkylsulphonic acid type. It is preferred to use compounds which do not form complexes with iron ions in alkaline solution. Aminoalkylcarboxylic acids with up to about 10 C-atoms have proved to be particularly suitable. Examples of such compounds are ethylene diaminotetracetic acid, nitrilotriacetic acid and diethylene triaminopentacetic acid.

Although it is already known in principle to add such compounds to developers, they serve in the known cases as sequestering agents or water softeners. The developers according to the invention are clearly distinguished from these prior developers since they contain the above additives in much larger quantities than would be necessary for water softening. When water which has a degree of hardness of about 30 German hardness degrees, 1 German hardness degree, 1 dH=1O mg. CaO or 7.14 mg. MgO per liter of water, 1 dH=1.25 British hardness degree is used, a quantity of 1.2 g. of ethylene diaminotetracetic acid or nitriletriacetic acid per liter of developer is, for example, sufiicient to prevent precipitation of calcium or magnesium salts. The developers according to the invention contain at least 5 times the usual quanties used of these compounds.

A developer concentrate according to the invention is characterized by the following constituents per liter of concentrate:

G. Potassium salts (in the form of potassium hydroxide, potassium carbonate, potassium sulfite, potassium bromide, and others) 300-600 Hydroquinone, if desired in combination with other developers 20-80 Compounds according to the invention, for example, nitrile-triacetic acid, per g. of potassium salt 10-20 Apart from hydroquinone, other developers, especially of the pyrazolidone-(3) series, may be used, in particular 1-phenyl-pyrazolidone-(3).

Compounds which may be used for this purpose also include aminophenols, for example, methylaminophenol, 3-irnino-pyrazolidine or 4-aminopyrazolidone-(5) derivatives.

EXAMPLE 1 cc. of a developer concentrate of the' following composition:

G. Potassium sulfite 312 Potassium hydroxide 15 Potassium carbonate 90 Hydroquinone 45 1-phenyl-pyrazolidone-(3) 1.5 Potassium bromide 10 Ethylene diaminotetracetic acid 8 Distilled water up to 1 l.

are diluted to seven times the quantity with water of about 30 German degrees of hardness. The quantity given above of ethylene diaminotetracetic acid is sufficient for complex formation of calcium or magnesium salts and no precipitates of this type appear.

For comparison other developers were used which mixtures correspond to the above composition but contained in addition, per liter of the above dilute, ready-to-use developer, 2.4 g., 3.6 g. and 6 g. of ethylene diaminotetracetic acid. The pH of these developers used for comparison was adjusted to that of the mixture given above by the addition of a small amount of aqueous potassium hydroxide. The pH of all the developers was 10.7.

When the developers were used in the usual way (by developing photographic copy papers therein) cloudiness appeared after a relatively small throughput in all developers except that one which contained 6 g. of ethylene diamino tetracetic acid, this cloudiness rendering further use of the developer impossible. The first precipitates appeared after throughputs of only 2-3 m? of exposed paper per liter.

In the developer according to the invention, which contained an additional 6 g. of ethylene diaminotetracetic acid per liter of ready-to-use developer, no cloudiness was 3 detected even after a throughput of 6 m. of paper per liter of developer, i.e., when the developer effect was exhausted.

Similar results were obtained when instead of ethylene diaminotetracetic acid, comparable quantities of nitriletriacetic acid or diethylene triaminopentacetic acid were used.

What is claimed is:

1. In a photographic silver halide developer composition containing a silver halide developing agent and potassium compounds providing alkalinity and'stability and which is substantially free of sodium compounds, the im provement according to which the developer contains a sequestering amino-acetic acid in a concentration of from about 10 to 20 grams for every 100 grams of potassium salts.

2. The combination of claim 1 in which the developer is an aqueous concentrate.

3. The combination of claim 1 in which the sequestering acid is ethylene diamino tetracetic acid, nitrile-triacetic acid or diethylene triamino pentacetic acid.

References Cited UNITED STATES PATENTS 2,891,861 6/1959 Welliver 9666.5 2,915,394 12/1959 Krizka 9666.4

, FOREIGN PATENTS 725,573 3/1955 Great Britain.

' OTHER REFERENCES Gauvin, H.: CA 45:3269a, Sci. et. Inds. Phot., 22, 416 (1951).

Gauvin, H.: CA 47:7353f, Compt. vend., 236, 8079 (1953).

NORMAN G. TORCHIN, Primary Examiner 

